Maintenance of high extracellular pH does not influence cell pH or metabolism in submerged anoxic bullfrogs

Abstract

We compared extracellular and intracellular acid-base states in paralyzed bullfrogs subjected to 4 h of anoxic submergence at 15 degrees C with or without maintenance of extracellular pH at preanoxic levels by bicarbonate infusion. We also assessed anaerobic metabolism under these conditions by measuring tissue lactate and glycogen concentrations in liver, heart, and skeletal muscle. Although bicarbonate infusion resulted in a significantly higher arterial blood pH (pHe) than saline infusion, intracellular pH (pHi) of heart and skeletal muscle, as determined by the DMO equilibration technique, were not significantly different after 4 h of anoxia. We were also unable to demonstrate any differences in anaerobic metabolic rate, since both tissue lactate accumulation and glycogen depletion were identical in bicarbonate- and saline-infused frogs in the tissues studied. We conclude that (1) alterations in the extracellular acid-base state by bicarbonate infusion are not necessarily reflected in the intracellular compartment, perhaps due to powerful intracellular buffering processes, and (2) maintenance of an alkaline extracellular pH during anoxia in bullfrogs does not influence the anaerobic metabolic rate. We could not, however, rule out a possible role for intracellular pH in regulating anaerobic metabolism during anoxia in frogs.

The role of mineralized tissue in the buffering of lactic acid during anoxia and exercise in the leopard frogRana pipiens

“…The sampled structure had a milky appearance that was consistent with earlier descriptions of the endolymphatic system. Both exercise and anoxia increased lactate concentrations in all tissues examined to levels observed in previous studies (Andersen and Wang, 2003;Armentrout and Rose, 1971;Bennett and Licht, 1974;D'Eon et al, 1978;Donohoe and Boutilier, 1999;Hutchison and Turney, 1975;Warburton et al, 1989;Wasser et al, 1993Wasser et al, , 1991Wegener and Krause, 1993). With the exception of gastrocnemius and heart, plasma had a higher lactate concentration than the other tissues examined, as has also been observed in cold hypoxic frogs (Donohoe and Boutilier, 1999) and cold anoxic turtles (Jackson et al, 1996).…”

Alterações da taxa metabólica por provimento de oxigênio advindo de alterações do sistema circulatório e respiratório e por substratos da cadeia de transporte de elétrons mitocondrial

“…Apesar do estudo mostrar aumento no uso do metabolismo anaeróbico com 3h de hipóxia em cérebros isolados de girinos (98 % N2/2 % CO2) (Winmill, Chen, Hedrick, 2005), no corpo inteiro, a queda na concentração de oxigênio parece ser mais gradual, como observado no indicativo de anaerobiose, com 12 h de exposição. L. catesbeianus é conhecida por sobreviver a anóxia à baixas temperaturas (Wasser et al, 1993). Além disso, a temperatura utilizada nos experimentos 20-26º C, proporcionou o aumento no consumo de oxigênio que aumenta com uma maior temperatura (Rocha, Branco 1997), contribuindo para a morte dos grinos.…”